BIBLIOGRAPHY

Z. G. PINSKER. Electron Diffraction. Edited and with a preface by Academician A. A. Lebedev. Publishing House of the Academy of Sciences of the USSR, 1949, 404 pp., 153 figs.

The phenomenon of electron diffraction played a most important role in the establishment of quantum mechanics. In the first years after its discovery, experiments on electron diffraction were carried out to test quantum-mechanical theories. Soon, however, it became clear that the interaction of electron beams with matter makes it possible to obtain very valuable information on the structure of matter, information inaccessible by any other method. In parallel with the study of the phenomenon of electron diffraction itself, therefore, electronography began to develop—the doctrine of the method of investigating the structure of matter by means of electron beams.

The book under review is devoted to the whole problem as a whole; it considers both the theory and the experimental investigations of electron diffraction, as well as electronography.

The book consists of 14 chapters. In Chapter I the reader is reminded of the basic facts of wave mechanics, and in the exposition the author follows the works of Fock.

Chapter II considers the classical theory of wave diffraction on linear, two-dimensional, and three-dimensional lattices. In the last paragraph the concept of structural amplitude is introduced. The purpose of the chapter is to substantiate the geometrical conditions of diffraction, which are formulated both in the direct and in the reciprocal lattices.

Chapters III and IV discuss experimental technique. The principles of the experiment are given in Chapter III; in the following chapter the designs of electron diffraction cameras are discussed in detail. The author’s extensive experience makes this chapter very interesting. All details and parts of the electron diffraction camera are given in diagrams and drawings. The author does not forget to dwell on the “minor details” essential for the successful operation of the electron diffraction camera. Very valuable is the detailed consideration of electron diffraction camera designs manufactured in the central laboratories of the Soviet Union. These examples serve as the basis for discussion of design details.

Chapter IV considers not only the construction of the electron diffraction camera, but also the best schemes for powering the installation, as well as the experimental technique for preparing specimens.

Chapter V is one of the most essential for electronography—it is devoted to the calculation of electron diffraction patterns. After a brief introduction, an extensive paragraph sets forth methods for indexing spot electron diffraction patterns. Here one would like somewhat greater clarity and fuller detail. The author makes wide use of the reciprocal lattice in explaining diffraction phenomena. The author’s own work on determining by this method the lattice period in the direction of the beam is presented well and clearly (pp. 94–95). Therefore one would like the book to contain an introductory paragraph in which questions of the form and dimensions of the nodes of the reciprocal lattice and the degeneration of nodes into lines and planes would be discussed. The presence

Bibliography

The inclusion of such a paragraph would have made unnecessary such pages of the book as 7–88, and would have made it possible to conduct the subsequent exposition more compactly and clearly.

Be that as it may, on the basis of the material presented, Chapter V is of great interest. Perhaps too much space is devoted to electron diffraction patterns from a rotating specimen.

Chapter VI is devoted to the refraction of electron waves and to the determination of the internal potential of a lattice. In the first section, the geometrical changes in the diffraction conditions that occur owing to refraction are discussed. In the next section the connection is discussed between the internal potential of the lattice, which determines refraction, and the work function of electrons in thermionic emission. Experimental material concerning the mean internal potential in a crystal lattice is collected in the last section.

In the following chapter the formula for the atomic factor is derived and experimental methods for determining this important factor are considered. New experimental data of Soviet authors are presented, showing sufficiently good agreement between theory and experiment, in any case for light atoms. This is an important circumstance for the further development of structural electron-diffraction work.

Chapter VIII sets forth the dynamical theory of the scattering of electron beams in a crystal. As everywhere in the book under review, the theoretical exposition is followed by data from experimental verification.

The next three large chapters (about 150 pages) are devoted to electron diffraction proper.

The application of electron beams to the investigation of the structure of matter embraces a considerable number of mutually unrelated fields. The structure of thin films, the properties of surfaces, the investigation of the atomic structure of crystals, the study of polymers—this, in the broadest outline, is the list of structural problems considered in the monograph under review.

The author describes not only the electron-diffraction methodology for studying particular specific problems; all the more so because the method of investigation itself retains, in general, the same features. Rather, he gives quite complete reviews of theory and of experimental data. This circumstance, undoubtedly, broadens to a very high degree the circle of readers of the book. At the same time, it is clear that the coherence of the book suffers somewhat from such an exposition. It is no longer only a doctrine of electron diffraction and of methods for investigating structures by electron beams, but also an exposition of the results of this investigation. Since, for a number of results obtained not by means of electron diffraction, the author, of course, does not present them, certain pieces from a course on the structure of matter, physical chemistry, etc., are “torn into” the book.

However, the author’s desire to make his monograph an encyclopedia in the field of electron-diffraction work, as A. A. Lebedev noted in his preface, to a considerable extent justifies this.

Very interesting material is presented in Chapter IX, devoted to the structure of thin films and surface layers. Here investigations are considered of the structure of thin films formed by the deposition of a substance both on an amorphous substrate and on the face of a single crystal. It seems to us especially interesting and promising to study oriented crystallization on single-crystal faces. The author has allotted to this new question a place corresponding to its importance.

In the case of sublimation of a substance onto a cellulose or other amorphous substrate, a very finely crystalline powder is formed. In connection with this the author examines in detail methods for determining grain sizes.

Chapter X is devoted to the study, by means of electron beams, of the atomic structure of crystals. The author calls this chapter “investigation of fine structure.” This term, which is sometimes used, seems to us unsuccessful.

In Chapter X data are presented on electron-diffraction studies of elements, oxide films, and layered lattices of the cadmium iodide type. The possibility of applying electron diffraction to the solution of complex structural problems is considered on two examples. The last paragraph gives a survey of works on the determination, by the electron-diffraction method, of the structures of organic compounds.

Questions concerning the study of oxide films, which are of great practical importance, ought to have been set apart in a separate chapter. In the direction of the research and in the results obtained, this material does not belong to classical structural work. There are many examples in which electron diffraction has been used to determine the atomic structure of a crystal. The author shows quite convincingly the possibility of carrying out a complete structural investigation of complex compounds.

In the chapter on the scattering of electrons by molecules, determinations of the structure of gas molecules and some work on polymers are set forth. A complete summary is given of all data on interatomic distances obtained by the electron-diffraction method. In our opinion, the method of electron-diffraction study of gases suffers from many shortcomings that are insufficiently emphasized by the author. The accuracy of this method is undoubtedly overestimated and awaits objective verification. The chapter under discussion ends with a short paragraph on molecular scattering in crystals. This very interesting question has not yet been studied at all; the rather controversial material cited by the author in this paragraph might perhaps have been omitted.

Chapter XII deals with the practically important problem of the structure of polished surfaces and lubricants. The discussion of the depth of transformations occurring during polishing is very interesting. The exposition of electron diffraction ends with this chapter. Chapter XIII is devoted to the diffraction of slow electrons, and Chapter XIV to the polarization of electrons. At the end of the book are placed three mathematical appendices and a bibliography of several hundred titles.

The book embraces a broad range of questions; it will be of interest both to experimentalists and to theoreticians, to physicists and chemists concerned with the structure of matter.

Soviet science has played a major role in the development of studies of electron diffraction and electronography. In many sections the first works were carried out in the Soviet Union, and in almost all branches of electronography and related fields Soviet scientists have done much that is new and interesting.

The author has taken care that this picture should stand out vividly before the reader’s eyes, and he has achieved his aim.

There are errors and misprints in the book; however, they are few. In one place, instead of dichloroethylene, dichloroethane is printed; in another place (p. 338), apparently, a missed or transposed line is present, and so on.

It is necessary to note the exceptionally good production of the book. The numerous inserts, with remarkable clarity, show the reader the fine details in the electron diffraction patterns obtained by the author. The Soviet book market has received a useful book.

A. Kitaigorodskii